Add unit test and supporting code to test process overflow case.

chrome/browser/renderer_host/render_process_host.cc

Index: chrome/browser/renderer_host/render_process_host.cc
diff --git a/chrome/browser/renderer_host/render_process_host.cc b/chrome/browser/renderer_host/render_process_host.cc
index 5f9363e643ce4bff8c76fe877110ff2bf8e82693..959252efd9fcd189a90d74d5d133595f46d723d5 100644
--- a/chrome/browser/renderer_host/render_process_host.cc
+++ b/chrome/browser/renderer_host/render_process_host.cc
@@ -13,7 +13,12 @@
 
 namespace {
 
+size_t max_renderer_count_override = 0;
+
 size_t GetMaxRendererProcessCount() {
+  if (max_renderer_count_override)
+    return max_renderer_count_override;
+
   // Defines the maximum number of renderer processes according to the
   // amount of installed memory as reported by the OS. The table
   // values are calculated by assuming that you want the renderers to
@@ -74,8 +79,14 @@ IDMap<RenderProcessHost> all_hosts;
 
 }  // namespace
 
+// static
 bool RenderProcessHost::run_renderer_in_process_ = false;
 
+// static
+void RenderProcessHost::SetMaxRendererProcessCount(size_t count) {
+  max_renderer_count_override = count;
+}
+
 RenderProcessHost::RenderProcessHost(Profile* profile)
     : max_page_id_(-1),
       fast_shutdown_started_(false),